Java Generics 简明教程
Java Generics - Generic Methods Erasure
如果使用了无界类型参数,Java 编译器将用对象替换泛型类型中的类型参数,如果使用了有界参数,则用类型替换方法参数。
Example
package com.tutorialspoint;
public class GenericsTester {
public static void main(String[] args) {
Box<Integer> integerBox = new Box<Integer>();
Box<String> stringBox = new Box<String>();
integerBox.add(new Integer(10));
stringBox.add(new String("Hello World"));
printBox(integerBox);
printBox1(stringBox);
}
private static <T extends Box> void printBox(T box) {
System.out.println("Integer Value :" + box.get());
}
private static <T> void printBox1(T box) {
System.out.println("String Value :" + ((Box)box).get());
}
}
class Box<T> {
private T t;
public void add(T t) {
this.t = t;
}
public T get() {
return t;
}
}
在这种情况下,Java 编译器将用 Object 类替换 T,在类型擦除之后,编译器将生成以下代码的字节码。
package com.tutorialspoint;
public class GenericsTester {
public static void main(String[] args) {
Box integerBox = new Box();
Box stringBox = new Box();
integerBox.add(new Integer(10));
stringBox.add(new String("Hello World"));
printBox(integerBox);
printBox1(stringBox);
}
//Bounded Types Erasure
private static void printBox(Box box) {
System.out.println("Integer Value :" + box.get());
}
//Unbounded Types Erasure
private static void printBox1(Object box) {
System.out.println("String Value :" + ((Box)box).get());
}
}
class Box {
private Object t;
public void add(Object t) {
this.t = t;
}
public Object get() {
return t;
}
}
在两种情况下,结果都是相同的 −